scispace - formally typeset
Search or ask a question
Journal ArticleDOI

Living free-radical polymerization by reversible addition - Fragmentation chain transfer: The RAFT process

TL;DR: The authors proposed a reversible additive-fragmentation chain transfer (RAFT) method for living free-radical polymerization, which can be used with a wide range of monomers and reaction conditions and in each case it provides controlled molecular weight polymers with very narrow polydispersities.
Abstract: mechanism involves Reversible Addition-Fragmentation chain Transfer, and we have designated the process the RAFT polymerization. What distinguishes RAFT polymerization from all other methods of controlled/living free-radical polymerization is that it can be used with a wide range of monomers and reaction conditions and in each case it provides controlled molecular weight polymers with very narrow polydispersities (usually <1.2; sometimes <1.1). Living polymerization processes offer many benefits. These include the ability to control molecular weight and polydispersity and to prepare block copolymers and other polymers of complex architecturesmaterials which are not readily synthesized using other methodologies. Therefore, one can understand the current drive to develop a truly effective process which would combine the virtues of living polymerization with versatility and convenience of free-radical polymerization.2-4 However, existing processes described under the banner “living free-radical polymerization” suffer from a number of disadvantages. In particular, they may be applicable to only a limited range of monomers, require reagents that are expensive or difficult to remove, require special polymerization conditions (e.g. high reaction temperatures), and/or show sensitivity to acid or protic monomers. These factors have provided the impetus to search for new and better methods. There are three principal mechanisms that have been put forward to achieve living free-radical polymerization.2,5 The first is polymerization with reversible termination by coupling. Currently, the best example in this class is alkoxyamine-initiated or nitroxidemediated polymerization as first described by Rizzardo et al.6,7 and recently exploited by a number of groups in syntheses of narrow polydispersity polystyrene and related materials.4,8 The second mechanism is radical polymerization with reversible termination by ligand transfer to a metal complex (usually abbreviated as ATRP).9,10 This method has been successfully applied to the polymerization of various acrylic and styrenic monomers. The third mechanism for achieving living character is free-radical polymerization with reversible chain transfer (also termed degenerative chain transfer2). A simplified mechanism for this process is shown in

Content maybe subject to copyright    Report

Citations
More filters
Journal ArticleDOI
TL;DR: In this article, a review of recent mechanistic developments in the field of controlled/living radical polymerization (CRP) is presented, with particular emphasis on structure-reactivity correlations and "rules" for catalyst selection in ATRP, for chain transfer agent selection in reversible addition-fragmentation chain transfer (RAFT) polymerization, and for the selection of an appropriate mediating agent in stable free radical polymerisation (SFRP), including organic and transition metal persistent radicals.

2,869 citations

Journal ArticleDOI
TL;DR: A review of living radical polymerization achieved with thiocarbonylthio compounds by a mechanism of reversible addition-fragmentation chain transfer (RAFT) is presented in this article.
Abstract: This paper presents a review of living radical polymerization achieved with thiocarbonylthio compounds [ZC(=S)SR] by a mechanism of reversible addition–fragmentation chain transfer (RAFT). Since we first introduced the technique in 1998, the number of papers and patents on the RAFT process has increased exponentially as the technique has proved to be one of the most versatile for the provision of polymers of well defined architecture. The factors influencing the effectiveness of RAFT agents and outcome of RAFT polymerization are detailed. With this insight, guidelines are presented on how to conduct RAFT and choose RAFT agents to achieve particular structures. A survey is provided of the current scope and applications of the RAFT process in the synthesis of well defined homo-, gradient, diblock, triblock, and star polymers, as well as more complex architectures including microgels and polymer brushes.

2,127 citations

Journal ArticleDOI
TL;DR: A general overview of the preparation, characterization and theories of block copolymer micellar systems is presented in this paper, with examples of micelle formation in aqueous and organic medium are given for di-and triblock copolymers, as well as for more complex architectures.

1,856 citations


Cites background or methods from "Living free-radical polymerization ..."

  • ...[34] Chiefari J, Chong YK, Ercole F, Krstina J, Jeffery J, Le TPT, Mayadunne RTA, Meijs GF, Moad CL, Moad G, Rizzardo E,...

    [...]

  • ...An extension to CRP is the ‘reversible addition– fragmentation transfer’ (RAFT) technique pioneered by Rizzardo and co-workers [34,35]....

    [...]

Journal ArticleDOI
Fu Liu1, N. Awanis Hashim1, Yutie Liu1, M.R. Moghareh Abed1, Kang Li1 
TL;DR: A comprehensive overview of recent progress on the production and modification of polyvinylidene fluoride (PVDF) membranes for liquid-liquid or liquid-solid separation can be found in this article.

1,776 citations

References
More filters
Journal ArticleDOI
TL;DR: An extension of ATRA to atom transfer radical addition, ATRP, provided a new and efficient way to conduct controlled/living radical polymerization as mentioned in this paper, using a simple alkyl halide, R-X (X = Cl and Br), as an initiator and a transition metal species complexed by suitable ligand(s), M t n /L x, e.g., CuX/2,2'-bipyridine, as a catalyst.
Abstract: An extension of atom transfer radical addition, ATRA, to atom transfer radical polymerization, ATRP, provided a new and efficient way to conduct controlled/living radical polymerization. By using a simple alkyl halide, R-X (X = Cl and Br), as an initiator and a transition metal species complexed by suitable ligand(s), M t n /L x , e.g., CuX/2,2'-bipyridine, as a catalyst, ATRP of vinyl monomers such as styrenes and (meth)acrylates proceeded in a living fashion, yielding polymers with degrees of polymerization predetermined by Δ[M]/[I] 0 up to M n ≃ 10 5 and low polydispersities, 1.1 < M w /M n < 1.5. The participation of free radical intermediates was supported by analysis of the end groups and the stereochemistry of the polymerization. The general principle and the mechanism of ATRP are elucidated. Various factors affecting the ATRP process are discussed.

1,628 citations

Book
01 Jan 1995
TL;DR: In this article, the authors introduce a free radical reaction pathway for combination pathways for disproportionation combination vs disproportionation summary, and a termination termination pathway for termination pathway with oxygen initiator efficiency cage reaction and by-products.
Abstract: Part 1 Free radical reactions: introduction addition to carbon-carbon double bonds steric factors polar factors bond strengths theoretical treatments hydrogen atom transfer polar factors stereoelectronic factors reaction conditions abstraction vs addition summary radical-radical reactions pathways for combination pathways for disproportionation combination vs disproportionation summary Part 2 Initiation: introduction the initiation process reaction with monomer fragmentation reaction with solvents, additives or impurities effects of the reaction medium on radical reactivity reaction with oxygen initiator efficiency cage reaction and initiator-derived by-products primary radical termination transfer to initiator initiation in heterogeneous polymerization thermal initiation the radicals carbon-centred radicals oxygen-centred radicals Part 3 Propagation: introduction stereosequence isomerism - tacticity monoene polymers conjugated diene polymers structural isomerism - rearrangement cyclopolymerization ring-opening polymerization intramolecular atom transfer propagation kinetics and thermodynamics Part 4 Termination introduction radical-radical termination termination kinetics disproportionation vs combination - general considerations disproportionation vs combination - summary chain transfer mechanisms transfer agents transfer to monomer transfer to polymer inhibition and retardation "stable" radicals oxygen Part 5 Copolymerization: introduction statistical copolymerization copolymerization mechanisms block and graft copolymerization end-functional polymers block and graft copolymer synthesis Part 6 Controlling polymerization: introduction "defect structures" in polystyrene "defect structures" in poly(methyl methacrylate) controlling propagation solvent Lewis acids and inorganics template polymers compositional heterogeneity in copolymers agents for controlling termination organosulfur iniferters hexasubstituted ethanes and azo compounds alkoxyamines and related species

415 citations

Journal ArticleDOI
TL;DR: In this paper, the possibility of the synthesis of well-defined polymers by radical polymerization is discussed, and it is shown that the preparation of polymers with controlled macromolecular structure in a living radical process requires low stationary concentration of growing radicals which are in a dynamic equilibrium with dormant species.
Abstract: : Possibility of the synthesis of well-defined polymers by radical polymerization is discussed. Kinetic analysis demonstrates that the preparation of polymers with controlled macromolecular structure in a 'living' radical process requires low stationary concentration of growing radicals which are in a dynamic equilibrium with dormant species. Three approaches are described. First, when growing radicals react reversibly with scavenging radicals to form covalent species, second when growing radicals react reversibly with covalent species to produce persistent radicals and the third in which growing radicals participate in the degenerative transfer reaction which regenerates the same type of radicals. Some of the reported 'living' radical systems are critically evaluated.

224 citations